Signaling system



16, 1930. J. F. FARRINGTON I 1,784,867

SIGNALING SYSTEM Original Filed July 31, 1923v M-ZZ 24 Eng,

//v VEN TOR ATTORNEY ED STATES;

-;PATeT I JOHN F. FABRINGION, or rnusnme, new Yong; Assmnon no wnsmnnnnnnemnto centennial, moonronn'rnn, or new YORK. n. A oonronemionon NEW'YQRK SIGNALING SYTEM Original aeplication filed July 31,, 1923, Sari a-1M 6 4,2 jliqtentfie' 2 ,917 meanest. 0, 9

' i Divided and, this application filed June 192?. $eria1 No. lafiflsfi.

T pres t inve tion whites ta eee s systems and particularly to two-Way signal.- ing systemsemploying successive detection of carrier aves, as for-ezzaiuple, duplex radio telephonesyste ns,using double detection receiving circuits. 1

. Th pitin ipal, Obi of the i vent o is 99 prevent the transmitter at one end of such systems from causing disturbances in ree e at tha ndi a v T is. epiel atien is d ien rP iea ies erial N $54,823, filed. uly 31 9 23, a n Ne: 15 an? greet d August 20, 1929. I 1

A pet tion t the su je t atter d seri d and ed liereinis di cl sed in my wre h ing application Serial No. 326,986, filed September 27 1919, Patent No. 1,738,235, granted December 3,1929.

In the i l t ative einhedim l s Qt the l1- vent on shown and de crib i d tail here inafter, an oscillator connected to-a transmit ting and receiving antenna generates an outgoing carrier Wave and serves also in receiving, as a heterodyne oscillator and high frequency detector. Means are provided for connecting to it, in cei'ijugate relation to each other, a receiving path and a sending path, the receiving path including an intern liate frequency deteetor'and a telephone receiver, and the transmittingxpath including a microphone and means for causing signal modulation of the outgoing carrier-Wave. This conjugate relation prevents the modulating cur rent from causing disturbances in the receiver, although proper side tone effect is provided by detection of the modulated intermediate frequency carrier Wave resulting from the heating action between the unmodulated carrier wave collected by the antenna and the outgoing modulated carrier wave,

Figs. 1 and 2 are circuit diagrams of two forms of the invention.

Description 0/ Fefg,1.-,.iThe transmitting system in Fig. 1 comprises an antenna 7 to which iscon'nected arvacuum tube OTB-@715 in a well-known manner as illustrated, where: by oscillations are produced in the antenna at a frequency approximately equal to the natu ral frequency determ ned by the series arrangement comprising the capacity of the radieting member 7 the'inductanc'je of the coil 16 and the capacity of the condenser 17.. The

frequency of these oscillations may be desigsated in: Ther u f f1 maybe 500,000 eyles/$ e,'f0 e p e SPm 'n f thetEI QQ OD15 ispro-vided by the source 18, through the speech frequency choke coil 1 9, the circuit 20, andthe high frequency cholge 'coil2 l. The choke coil 21 offershigh impedance to both the incoming and outgor ing high frequency Waves shunted around the source 18 and the coil 19 is "the anodecathode path of'a vacuum tube M22; The input circuit 23 of thetuhe M-"- 22 'is coupled to a rnicrophone circ uit 24 which represents any suitable'sour'ce of speech or other signaling frequency electrical Waves or variations; The frequency of; these variations may be designated 5 'Ihe" production of speech tatt e Q 91 it'2 Will caus e n Stand ng vari tion in th impedance of h ltd-e22, will in turn cause'a correspondingvariation in the current supplied action eoil 19; This Willcause the'high frequency aves generated in the'antenna by theoscillating tube Q D.-l5 to" be varied or 'modulated in amplitudin accordance with the Waves produced in theicircuit 24; The

frequency of the resulting modulated current is herein designated by the expression his This symbolic manner of designating a modulated Wave Will used throughout this specification; modulated Wave so designated may or may not contain an unmodulated carrier component. In the operation of the systems of Figs; 1 and 2, the'transmitted modulated vvave does include such-unmodulated ca ri r component ion ence frequencies. Thus, if the incoming wave is a carrier wave of frequency f modulated at times by speech waves 8 and if frequency 7', equals 500,000 cycles and 7; equals 530,000 cycles, then circuit will be adjusted to be resonant at 30,000 cycles; and owing to the detecting or demodulating action ofthe oscillating tube O-D15 which has its anode- I cathode circuit connected to circuit 20 there will occur, in circuit 20, oscillations having a component with a frequency of 30,000 cycles and a wave of thisauxiliary carrier frequency modulated in accordance with the speech signal 8 or the signal .9 or by both of them 111 case both are being simultaneously transmitted. This is represented by the legend adj acentja circuit 20,.which is coupled to the circuit 20 and Which is tuned to and selects the auxiliary -or intermediate carrier frequency. The currents of the intermediate carrier frequency in the circuit 20' are amplified by meansiof a suitable amplifying device A-31 and then passed trough'any suit able filter, 32 to the detector D'l2,'the output circuitof which, includes a suitable in circuit 25 may be most advantageously tuned to be resonant at the auxiliary carrier frequency. This prevents a loss of energy of the auxiliary carrier frequency duejto the voltage drop across the tube M-22.

j The branch circuit 8 which is connected to the antenna, is intended to give the anten- .na one natural period equal to the mean pe riod of the incoming waves-from the distant station which are represented by the legend is An anti-resonant circuitB is serially included in the branch 8 andturned tothe transmitting carrier frequency f in order to prevent current of that frequency, or of-the frequencies of the outgoing waves whlch are. impressed on antenna 7, from passing through the branch 8. Any suitable tuning circuit or tuning means 10is also provided in the branch 8 whereby the said branchmay be given any desired rea-ctance which is necessary to tune the antenna for the incoming waves.v 7

An important; feature ofthis arrangement is that the frequency of the waves being transmitted is determined by and can be varied by the adjustment of the coil 16 and the condenser 17. After establishing the outgoing carrier at the desired frequency and adjusting circuit B to this frequency, the tuning reactance means 10 may be varied within considerable limitswithout producing a material variation of the waves being generated by the tube OD-l5 in the antenna. v If desired, the circuit 8 may be omitted ;but with the antenna tuned for the outgoingcar rier wave frequency incoming signals will then be received less efficiently.

If the space current path of tube M22, instead of being connected to circuit 20 and oscillator OD15 as shown in the drawmg, for supplyingspeech frequency voltage to the oscillating tube O-D15, be connected in theplace of balancing network 29, and the balancing network be then omitted, the voltage of speech frequency which is supplied to the oscillatingtube' from, the tube M-EZQ is impressed serially across the circuit 20. In some cases, this results in objectionable transients being set. up in circuit 20 which cause interferencewith the operation of the system. In order to avoid this, the circuit 20 is balanced for speech frequencies. The lead from th'e'plate of the tube M'22 is connected to an intermediate point 27 of the coil 28 and a balancing impedance network 29 is provided. This impedance network is of the'circuit from the point 27 through the oscillator OD15 to ground is equalto the time constant e E V R of the circuit frompoint 27 through the net work 29.to ground. a The network 29, therefore, constitutes an impedance which simulates the impedance of the plate-filament path of the oscillating tube O-D-l5 during its oscillating condition.

The elements 30 constitute a gridleak path for the oscillating tube OD-15 and com-v prise an inductance in series with a parallel combination of a resistance and a condenser.

Operation of Fig. 1.When signalsare be ing transmitted from the local station there is radiated from the antenna 7 a modulated carrier wave f is which is available for combination with the incoming signaling wave f i 8 to cause the transmission through circuits 20 and 20 of the wave This produces in the receiver 13 at any instant either or both of the signalss and 8 as indicated by the legend lei 8 2 an n;

' tone.

ja en t r e r, depending upo whether one or both are being transmitted at that instant. When no transmission of the signaling frequency is going Of u se, n y th medulate c mp nent of the outgoing carrier comhineswjith the incoming wave, to produce the auxiliary carrier wave. The auxiliary carrier frequency may be equal either to the sum or the difference of the principal carrier fre-, quencies, but since many practical advantages are attached to using the diiference'frequency rather than the sum frequency, this is the one which it has been assumed above is utilized. The amplitude of the intermediate or auxiliary carrier frequency wave impressed on the detector D12 is proportional to the product of the amplitudes of the principal carrier waves generated at the local and the distant stations, respectively. Thus, as? suming the same percentage of modulation at each station, the signal heard in the local receiver is of approximately the same intensity whether the local or distant station is signaling. In order to obtain a maximum indication from the distant station, it is consequently desirable to allow sufficient energy of the local carrier wave frequency to enter the receiving circuit to load the detector or the rectifying device such as D-12 with approximately the maximum energy input which it is capable of handling without material Signal distortion. The local energy is thus utilized as a desirable agent during the non-transmitting periods. The effects of interfering waves on the radio system are thereby, to a considerable extent,

overcome. V a

The transmitting operator will at once he comecognizant of an inoperative condition of his transmitting or re eiving system or that'of the distant transmitter, since the abs ce f side n effe Wi l rn the perator that the apparatus is not working properl lialancing the circuit 20 for speech quencies reduces the numberand amplitude of disturbing transients introduced in the receiving circuit and reduces the amplitude of speech frequency side tone directly in troduced into the receiving circuit.

Description of Fig. 2.Fig. 2 is similar to Fig. 1 but includes additional means to increase the selectivity and to reduce the side Corresponding elements in the two figures are identified by similar reference characters, and the letters 7 and s with appropriate subscripts are applied in \Fig. 2 with meanings similar to those in connection with Fig. 1. The selecting function of the tuned circuits 20 and 20, of Fig. 1 is here performed by a band pass filter 33 of a well-known type. The filter 33 selects a band of frequencies equal in width to the modulated Wave resulting from the combination of he incoming and outgoing Wave an substantially suppresses waves of other frequencies. The band pass filter 33is connected to the input circuit of an amplifier ALI-3e. To the output circuit of the amplifier is con nected a band pass filter 32 similar to filter 33 or otherwise constructed as maybe doi ed-M. 1

The filter 32 supplies the input circuit of an amplifi r A-35 which in turn feeds the detector D 12. It willthus be seen that the intermediate frequency which may be equal either to the sinner; the difference of the outgoing and incoming carrier waves is first selected by the band filter 33, amplified by the amplifier A r-34:, again selected by the filter 32 and again amplified by the amplifier A35. Such an arrangement is highly efiicient in selection and amplification. Additionalstages of amplification or additional selective means may be inserted in the circuit atany point. 1 i

By a tap 27 upon the coil 28 a balance of speech frequencies is obtained whereby the amount of speech frequency voltage intro duced into the filter 33 is reduced. The operation of the circuit of Fig. 2 will be apparentfrom the description above of the operation of Fig. 1, without further explanation. I

What is claimed is: a

1. A station for two-way communication systems comprising in combination, a, transmitting circuit including, 1 a source of signaling waves, a high frequency carrier wave source, and means for modulating said carrier waves in accordance with the signaling waves, means including a portion of said transmitting circuit for combining the energies of said carrier Waves, modulated at times,

with an incoming carrier wave, modulatcd'ut times, to produce a similarly modulated intermediate frequencyfcarrier wave, a receiving circuit for said intermediate frequency carrier wave, and means-conjugately relating portions of said transmitting and said receiving circuits, Y

2. A carrier wave transmission system" comprising a transmitting circuit, means connected .in said circuit for translating the transmitted wave and forcombining the transmitted wave with an incoming modulated carrier wave to produce a modulated intermediate frequency carrier wave, a circuit for transmitting,modulating waves to and said modulated intermediate frequency carrier Wave from said means, a source of modulating current in energy transfer relation to said last mentioned circuit, a modulated intermediate frequency carrier wave transfer circuit also in energy transferrelationwith said last mentioned circuit, and bah noing means for preventing the modulatitng waves from afiecting said transfer circui 3. A carrier wave transmission system comprising a transmitting circuit, means connected in said circuit for translating the transmitted wave and for combining the transmitted Wave with an incoming modulated carrier wave to produce a modulated intermediate frequency carrier wave, a circuit for transmitting modulating waves to and said modulated intermediate frequency carrier wave from-said means, a source of modulating current in energy transfer relation to said last mentioned circuit, a modulated intermediate frequency carrier ave transfer circuit also in energy transfer relation with said last mentioned circuit,-and balancing means for preventing the modulating waves from affecting said transfer circuit, said balancing means comprising an impedance which simulates the impedance, during its transmitting condition, of the path, including the transmitting circuit, from one terminal of the impedance to the other. I I

4. A transmitting and successive detection signaling system comprisin'ga two-way communication channel, a signal current channel and a receiving channel connected in substantially conjugate relationship to each other, and means comprising an oscillator detector circuit to connect conjugate channels in energy transfer relation to said two-way channel. I

5.'A signaling system comprising a twoway communication channel, a detectorincluded in said channel, a receiving channel, means included in said receiving channel for producing a second detection-of the detected wave from said first mentioned detector, a sending channel, and meansconnecting-said sending channel and said receiving channel to said two-way channel in substantially conjugate relation to each other.

6. A signaling system comprising two stations each of which includes a source of signal waves, a high frequency carrier; wave source, means for modulating the carrier wave generated by said source in accordance with the corresponding signal wave, means at least partially common to said high frequency carrier wave source for combining the energy of said carrier waves, each modulated at times, to produce a similarly modulated intermedie ate'frequency carrier wave, means for deriving the signal waves from said intermediate frequency carrier wave, and means substantially conjugately'relating said modulating means and said means for deriving the signal waves from said intermediate frequency carrier wave.

7 A station for two-way communication systems comprising in combination a trans mitting circuit and a receiving circuit, including a transmitting and receiving conductor, common means associated in energy transfer relation with said conductor for generating the outgoing high frequency carrier wave and for producing from the'incoming modulated high frequency carrier wave a similarly modulated intermediate frequency carrier Wave, amodulating circuit associated with said means for modulatingsaid outgoing high frequency wave, a device for detecting said intermediate frequency wave, and means substantially I conjugately relating portions of said transmitting and receiving circuits.

8. A carrier wavetransmission system to said last mentioned circuit,a detecting del vice, a tuned circuit connecting said detecting device in energy transfer relation to said last mentioned circuit, andbalancing means for preventing the modulating current from affecting said detecting device.

9.*A carrier wave transmission system comprising in combination, a'transmitting and receiving conductor,'commonmeans associatedwith said conductor for generating a high'frequency carrier wave'and for producing from the modulated carrier wave-received over said conductor a similarly modulated carrier waveof different frequency, a bandpass filter associated with said means for selecting the modulated carrier wave of said difierent frequency, an amplifier for amplifying said selected wave,'a bandpass filter-connectedto said amplifier for selectively transmitting said amplified wave, an amplifier for amplifying the latter wave, a detector connected to said latter amplifier, modu latingineans associated with said conductor and said first mentioned filter, and means substantially conj ugately vrelating said. modulating means and said firstmentioned filter. 10. 'A'combination for two-way signaling comprising a transmission means,'an=oscillator-modulator circuit, a source of signal currents and a receiver circuit both of which are associated with sald transmission means through said oscillator-modulator circuit;

ill) 

